| Cross-linked polyethylene(XLPE)cables with excellent insulation performance have been widely used in high-voltage DC transmission projects in China,but ordinary XLPE insulated cables have been difficult to meet the needs of China’s future power transmission development.Modification of polymers by nano-doping is an effective means to improve the performance of dielectric materials,and has been a hot research topic in the field of engineering dielectrics.Studies have shown that the doping of nano-zeolite with porous structure can significantly improve the insulation performance of polymers,but due to the high surface energy of nano-zeolite,agglomeration easily occurs in polymers,resulting in poor modification effect.Meanwhile,the low thermal conductivity of XLPE is easy to cause aging and damage of XLPE insulated cable in high temperature and high pressure working environment,which affects the safe operation of the cable.In this paper,in order to solve the problems of dispersion of nano zeolite in polymer materials and low thermal conductivity of XLPE,Preparation of TMPTAS-4A-HBP,a type 4A nano zeolite with cross-linking agent(TMPTAS)function,which is also grafted with hyperbranched polyarylamide groups(HBP)with high thermal conductivity on the surfaceand,it was doped into low-density polyethylene to prepare TMPTAS-4A-HBP/XLPE nanocomposites.Based on the principle of silica hydroxyl modification in nano-zeolite and Michael addition reaction of sulfhydryl-double bond,Grafting of hyperbranched polyaramid and auxiliary crosslinking agent onto the surface of nanozeolite.The successful preparation of TMPTAS-4A-HBP was confirmed by nuclear magnetic resonance hydrogen spectroscopy tests and infrared spectroscopy.Based on the principle of chemical cross-linking,TMPTAS-4A-HBP/XLPE nanocomposites were prepared by blending and pressing.The gel content test revealed that the gel content of TMPTAS-4A-HBP/XLPE nanocomposites was higher than that of pure XLPE and4A/XLPE nanocomposites,which confirmed that TMPTAS-4A-HBP/XLPE particles were successfully cross-linked into the three-dimensional mesh structure of XLPE;the scanning electron microscopy revealed that TMPTAS-4A-HBP nanoparticles in It was found by SEM that TMPTAS-4A-HBP nanoparticles had more uniform dispersion in XLPE matrix,which confirmed that the surface energy of nano-zeolite was reduced by surface modification.The effects of TMPTAS-4A-HBP nanoparticles on the electrical insulation and thermal conductivity of XLPE were investigated by comparative experimental methods,and the results showed that the characteristic breakdown field strength,electrical dendrite starting voltage,conductivity characteristic threshold field strength,dielectric constant and dielectric loss of TMPTAS-4A-HBP/XLPE nanocomposites were higher than those of pure XLPE and 4A/XLPE nanocomposites.Meanwhile,the introduction of TMPTAS-4A-HBP nanoparticles more obviously inhibits the occurrence and growth of XLPE electric dendrites and space charge injection and migration,which is mainly attributed to the more uniform dispersion of TMPTAS-4A-HBP in XLPE,thus increasing the interaction interface between nanoparticles and XLPE,and the trap density and energy level of nano-zeolite particles introduced into XLPE density and energy level increased;Moreover,the thermal conductivity of 3wt% TMPTAS-4A-HBP/XLPE nanocomposite is 7.11%,7.56%,7.40% and 6.82% higher than that of pure XLPE at 20℃,40℃,60℃ and80℃,respectively,mainly because the hyperbranched polyarylamide with high thermal conductivity properties is accessed into the cross-linked mesh structure of XLPE through TMPTAS-4A-HBP,Increasing the number of thermally conductive nodes in XLPE,and reduces the thermal resistance of the thermal path,thus improving the thermal conductivity of XLPE.The TMPTAS-4A-HBP/XLPE nanocomposite,not only the electrical insulation performance is significantly improved,but also the thermal conductivity is improved,which is significant for the development of XLPE high-voltage DC insulated cables. |
PDF Full Text Request